Dispersion of mineral matter



Patented Nov; 20,

DISPERSION or mar-41m MATTER Oscar Frederick Nitzke, Belmont, Mass.

No Drawing. Application March 18, 1932,

- l Serial No. 599,850

scams. (01. 134-1) This invention relates to the production ofdispersions of thermo-plas'tic hydrocarbon materials, such as petroleumasphalt, mineral asphalt and the like, in an aqueous medium.

The main purpose of the invention relates to the production ofdispersions of asphaltic material in an aqueous medium, which,dispersion will be of relative high stability and which may be dilutedsufficiently with water to have high penetration qualities, e. g., whenapplied in penetration type of road" work.

It is of importance in emulsions'of the type disclosed that thesaponifiable material employed can be readily obtained 'in' quantity andat a fair price in this country and that the material Will'not undulydetract from the quality of the asphalt after the emulsion has beenapplied a Q It has been found that vegetable pitches, such as stearinpitch, whichfis a fatty'acid pitch constituting the still residi'um'resulting from the distillation and" purificationof vegetable oils, such.as cottonseed oil, can be used to furnish the" pr'otectiVeCdlloid orstabilizer in emulsions of mineral asphalts and pitches. This residuumis available at cottonseed oil refineries, for example, substantially asa waste product, since it has only limited applications commercially,due to its relatively poor weathering qualities when used alone. Asavailable on the market the preferred form has a dark pitch-like bodyhaving approximately the following characteristics,- specific gravity of1.01, melting. point of 100 F. to 153 F. (Ball and Ring),-an acidnumberGO,

and a low unsaponifiable content, some .examples being as low asapproximately 5% to 8%. This material, known as stearin pitch incommerce, is completely miscible in any proportion with mineralasphalts, e. g; those derived from the distillation of crude petroleum.

In forming the emulsion, the asphalt and vegetable pitch are brought toa temperature sufficiently high to liquefy them and they are completelymixed as by being boiled with steam or by having air passed upwardlythrough the same to produce a homogeneous mixture of the mineral asphaltand vegetable pitch.

Since there is no tendency in the mixed materials to separate out onsolidification, the mixed materials may be permitted to return to asolid state thereafter and then reheated to a fluid state, at the timeof the formation of the dispersions. The dispersion may, however, beformed .,while the materials are heated, as soon as they have beenmixed, and without permitting them to cool.

The dispersion is formed by introducing the melt, comprising the asphaltand vegetable pitch, with agitation into a body' of water con taining asmall quantity of caustic soda or other alkali capable of serving as asaponifying agent for the saponifiable content of the melt. Thef causticsoda ih solution apparently reacts with such free fatty acidor fattyacid glycerides'as are present in -the stearin pitch to generate soapsinsitu' throughout the heat liquefied mix-i ture, these soaps serving tostabilize the parsc'les of bitumen reduced to small part'icle size bythea gitation when the melt is introduced-into the aqueous medium. Inthe present instance,- in addition to the'br'eaking up of the' materialsinto microscopic particles in the aqueous medium by the agitation whichaccompanies mixing the particles, I believe there is also a leaching outof the soluble soap produced inthe mass with the resultant release offine particles of re leased bitumen broken up by thele'aching ac can.I'n'anyevent I have foundthat the pa r'ti ole size of the resultingdispersion is very small.

While difierent vegetable pitches differ considerably in theircharacteristics, it has been found that usually there is about 15% to40% or higher by weight of the material which is saponifiable and whichmay be converted into soap functioning to stabilize the dispersion. Inpractice it is desirable to use as large a proportion of asphalt aspossible inthe' procurement of a stable dispersion. This is true becauseof the fact that as a rule asphalts are far more stable when subjectedto weathering than the vegetable pitches and most other stabilizingagents. If too small an amount of the vegetable pitch is used, thereresults a dispersion in which the particles tend to separate out andcoalesce so that the dispersion does not have the necessary stability,for example, for storage or transportation thereof.

It has been found that about 2 of stearin pitch based on the weight ofthe mineral asphalt 10c, dispersed affords a dispersion of relativelypoor stability, even though the materials are thoroughly saponified. Asthe ratio of the stearin sions containing from 2 to 10% by weight, basedon the mineral asphalt, provides a sufiicient range of stability in thefinal product for all usual purposes. The products formed within thisrange have sufficiently satisfactory bonding and weathering qualitiesfor most purposes and particularly for road building and maintenancework.

Within the above range an emulsion formed with 5% stearin pitch, basedon the quantity of mineral asphalt employed, affords a highly stableemulsion of excellent weather-proofing qualities and the finishedproduct can be diluted with water to as low as 50% to 60% solids contentwithout any marked tendency to coalescence or settling out of theparticles. An emulsion of this type can readily be mixed with roadbuilding materials, such as sand and crushed stone, and when applied tothe roadway the asphalt is found to have the bonding qualities requiredfor this type of work.

The following is an example of the formation and use of the emulsion forroad building purposes. A mixture of parts of mineral asphalt ofapproximately F. melting point and 150- 200 penetration value is meltedand thoroughly mixed with 5 parts of vegetable pitch, the mixture beingheated to approximately 300 F. The melt so prepared is then mixed withan equal volume of to /2% alkali metal hydroxide or carbonate watersolution heated to F. to F., forming an emulsion of 50% solids contentwith a temperature of approximately 195 F. The water content may be aslow as 30% of the final dispersion. The particles of an emulsion soformed are uniformly small, being ap roximately one ten-thousandths ofan inch in diameter.

The emulsion disclosed herein is particularly useful for penetrationtype of road work, wherein the materials are laid in place and theasphalt poured over, into and through the crushed stone and othermaterials. The emulsion has a propconditions, but in general theemulsion disclosed herein will break within about two hours after it hasbeen applied.

While the examples given have been relatively specific as required bythe statutes for a complete disclosure of the invention, it will beunderstood that they are intended as examples only, and that theinvention is to be limited only as set forthin the appended claims.

What I claim is:

1. The process of forming an aqueous dispersion of asphalt comprisingintimately mixing therewith from. 2% to 5% of stearin pitch having arelatively high saponification value and thereafter dispersing saidmixture, while heated, in a dilute aqueous solution of a non-stabilizingalkali, and forming through the reaction of said pitch and alkalireaction products constituting I.

the essential stabilizing elements of the dispersion.

2. A dispersion whose solids content consists of from 95% to 98% mineralasphalt and from 2% to 5% stearin pitch, of the nature of cotton seedoil foots pitch, dispersed in an alkaline aqueous medium, the alkalinityof which is supplied by less than 1%, based on the water content, of asubstantially non-stabilizing alkali of the nature of caustic soda, thedispersion being IL),-

stabilized essentially by the reaction products of said pitch and saidalkali.

OSCAR FREDERICK NEITZKE.

